A building, such as a home or other dwelling, typically includes critical and non-critical loads to the primary power supply of the building, which is generally a utility power supply. The critical loads for a home, for instance, may include the HVAC system, sump pump, refrigerators, freezers, dishwasher, washer/dryer, and life-sustaining medical equipment. Other loads of the home are generally considered non-critical. The non-critical loads are generally connected to non-critical branches that are hardwired to a load center, and the critical loads may be connected to critical branches that are hardwired to a separate subpanel; both of which are powered by the primary power supply during normal operation.
To ensure power to the critical loads during primary power supply failure or interruption, it is known to connect the subpanel and, thus, the critical loads (or at least the branches that feed those loads), to an auxiliary power supply, such as an electrical generator, using a transfer switch. Many prior art transfer switches are manually operated. With transfer switches of this type, the operator initiates operation of an auxiliary power supply, such as an electrical generator, and connects the auxiliary power supply to the transfer switch, unless there is a permanent connection between the generator and the transfer switch. The individual switches or circuit breakers of the transfer switch are then actuated to supply power from the auxiliary power supply to the circuits in which the individual switches are connected.
Conventional transfer switches use classical switching devices, such as double-throw switches or relays, linked single-throw switches or circuit breakers, linked contactors or relays, semiconductors (triacs, IGBTs, etc.), and the like. These classical switching devices perform two general functions: isolation and current making/breaking. In the case of the former, these classical devices electrically isolate the primary power supply and the auxiliary power supply from one another. This is critical to prevent backfeeding of power. Regarding the latter, when energizing a load, the switch for that load (or at least the branch to which that load is connected) must be moved from an OFF position to an ON position. When moved to the ON position, a classical switching device will close the circuit between the load and the power supply. Thus, when the switching device is moved to the ON position when there is a voltage across the switching device, the switching device will “make” current. Similarly, a classical switching device may be moved from the ON position to the OFF position to open the circuit between the load and the power supply and thereby “break” current. Such a classical device may perform this current breaking in response to a manually throwing of the device or may include an overload feature so that the device is “tripped” or automatically thrown to the OFF position when an undesirable current condition is detected.
Despite their widespread use, conventional transfer switches fall within this single class or type thereby reducing consumer choices and variability in designing a power management system for a building, home, or other dwelling.